EMERGENCE, LOCALIZATION AND MATURATION OF NEUROTRANSMITTER SYSTEMS DURING DEVELOPMENT OF THE RETINA IN XENOPUS-LAEVIS .1. GAMMA-AMINOBUTYRIC ACID

The high‐affinity uptake, biosynthesis and release of GABA have been studied in the retina of Xenopus laevis. In the mature retina, [3H]‐GABA is accumulated predominantly by horizontal cells. A second population of cells located in the inner nuclear layer (possibly a type of amacrine cell) also showed a specific GABA uptake. In addition, this retina contains significant activities of L‐glutamic acid decarboxylase and also releases [3H]‐GABA in response to increasing K+ concentrations in the medium. We have followed the appearance and maturation of these GABA‐ergic properties during embryonic development of this retina. Our results indicate that these properties emerge in a precise temporal pattern during retinal differentiation: the specific neuronal uptake of GABA synthesis which is followed by K+‐stimulated GABA release. Copyright © 1979 The Wistar Institute Press